# WBBSE Class 9 Physical Science MCQ Questions Chapter 7 Sound

Well structured WBBSE Class 9 Physical Science MCQ Questions Chapter 7 Sound can serve as a valuable review tool before exams.

## Sound Class 9 WBBSE MCQ Questions

Multiple Choice Questions :

Question 1.
What should be the minimum frequency of a vibrating body for producing sound?
(i) 2000 Hz
(ii) 100 Hz
(iii) 20 Hz
(iv) 150 Hz
20 Hz

Question 2.
How does pitch of sound depend on frequency ?
(i) pitch increases with decrease of frequency
(ii) pitch decreases with increase of frequency
(iii) pitch increases or decreases accordingly with increase or decrease of frequency
(iv) none of these.
Pitch increases or decreases accordingly with increase or decrease of frequency.

Question 3.
The unit of frequency is :
(i) ohm
(ii) mho
(iii) Hz
(iv) torr
Hz

Question 4.
Migraine is caused by –
(i) sound pollution
(ii) air pollution
(iii) water pollution
(iv) soil pollution.
sound pollution

Question 5.
When one end of a long iron pipe is struck –
(i) two
(ii) three
(iii) four sounds are heard.
Two

Question 6.
The relation between velocity (v) of a sound with its density (d) is :
(i) v ∝ $$\frac{1}{d}$$
(ii) v ∝ $$\frac{1}{\sqrt{d}}$$
(iii) v = $$\frac{1}{d}$$
(iv) v = $$\frac{1}{\sqrt{d}}$$
v ∝ $$\frac{1}{\sqrt{d}}$$

Question 7.
The relation between velocity (v) of a sound with the absolute temperature (T) is –
(i) v ∝ √T
(ii) v ∝ T
(iii) v = T
(iv) v = √T
v ∝ √T

Question 8.
If the size of the sounding body be bigger then intensity of sound will be :
(i) increased
(ii) decreased
(iii) remains same
increased

Question 9.
The velocity of sound through iron is –
(i) 4 times
(ii) 10 times
(iii) 15 times
(iv) 16 times than the velocity of sound through air.
15 times

Question 10.
The sensation due to short sound remains for about –
(i) $$\frac{1}{20}$$ second
(ii) $$\frac{1}{10}$$ second
(iii) $$\frac{1}{30}$$
(iv) $$\frac{1}{5}$$ second and is known as persistence of hearing.
$$\frac{1}{10}$$ second.

Question 11.
Relation among velocity (v), wavelength (λ) and frequency (v) is :
(i) v = v λ
(ii) v = v λ
(iii) λ = v\v
(iv) v = vλ
v = v\λ

Question 12.
If the velocity of a wave havingwave length 1.7 m is 340 m / s then what will be the frequency of the wave?-
(i) 20 Hz
(ii) 200 Hz
(iii) 2000 Hz
(iv) 100 Hz
200 Hz

Question 13.
If the tones present in a note are of frequencies 100,150,200,280, 300,450 and 500 , what is the fundamental tone ?-
(i) 100
(ii) 280
(iii) 500
(iv) 450
100

Question 14.
The sound of lightning is heard after 6 sec. it is seen. If the velocity of sound is 330 m/s at that time what will be the distance of the cloud?
(i) 1980 m
(ii) 2000 m
(iii) 330 m
(iv) 350 m
1980 m

Question 15.
Wave motion transfers –
(i) matter
(ii) energy
(iii) momentum
(iv) all of these
energy

Question 16.
Distance between two successive compressions is –
(i) $$\frac{\lambda}{2}$$
(ii) $$\frac{\lambda}{4}$$
(iii) λ
(iv) 2 λ
λ

Question 17.
Sound wave can travel –
(i) only in solid
(ii) only in liquid
(iii) only in gas
(iv) in all of these
in all of these

Question 18.
The speed of sound in air-
(i) decreases with the increase in temperature
(ii) remains the same with the increase in temperature
(iii) remains the same with the decrease in temperature
(iv) increases with the increase in temperature.
decreases with the increase in temperature.

Question 19.
Sound wave is –
(i) transverse in nature
(ii) longitudinal in nature
(iii) both transverse and longitudinal in nature
(iv) none of these
longitudinal in nature

Question 20.
Distance between a compression and a rarefaction is
(i) $$\frac{\lambda}{4}$$
(ii) $$\frac{\lambda}{2}$$
(iii) λ
(iv) 2λ
$$\frac{\lambda}{2}$$

Question 21.
Which of the following waves is a mechanical wave ?
(i) light wave
(ii) Sound wave
(iii) X-rays
(iv) Ultra-violet ray
Sound wave

Question 22.
The speed of sound is maximum in –
(i) air
(ii) hydrogen
(iii) water
(iv) iron
iron

Question 23.
In SONAR, we use –
(i) infrasonic
(iii) audible sound
(iv) ultrasonic
ultrasonic

Question 24.
Infra sound can be heard by –
(i) bat
(ii) rhinoceros
(iii) dolphin
(iv) human being
rhinoceros.

Fill in the blanks :

1. Sound moves ______ through solid than through liquid.
faster

2. Sound of frequency above is known as ultrasonic ______ sound.
20,000 Hz

3. The sound of frequency below 20 Hz is called ______ sound.
subsonic

4. Sound originates from a mechanically ______ body.
vibrating

5. We can hear sound only if the frequency of a vibrating body lies within the limits of ______ to 20,000 Hz.
20

6. The maximum displacement of a particle in a medium on either side of its mean position is known as ______.
amplitude.

7. Time period is the time required by a particle to make ______ complete oscillation.
one

8. The number of complete oscillations of a body per second is known as its ______ .
frequency

9. To perceive the initial and the reflected sounds clearly, the minimum time interval between these should be at least ______ second.
$$\frac{1}{10}$$

10. Pitch is the characteristic of a musical sound that distinguishes a sharp sound from a ______ sound.
flat

11. Pitch increases corresponding to ______ in wavelength.
decrease

12. Pitch of sound produced by a vibrating air column increases with the ______ of the air column.
length

13. Note is analogous to white or polychromatic light and ______ analogous to light of a single colour.
tone

14. In a note, the sound of least frequency is called the ______ tone.
fundamental

15. A ______ continuous noise of level may cause tension, headache, migraine, neurological diseases.
high

16. A ______ is necessary for the propagation of sound.
medium

17. If the frequency of sound is high, pitch of the sound will also be ______.
high

18. The particular harmonic whose frequency is double the fundamental frequency is called ______ of the fundamental.
octave

19. Sound is a form of ______ .
energy

20. A ______ medium is required for the propagation of sound.
material

21. The velocity of sound in a gas is proportional to the square root of the _______ of the gas.
density

22. The source of sound in laboratory is _______.
sonometer

23. _______ is the safe intensity of sound according to WHO.
45 decibel (or 45 dB)

24. Sound originates from a body that ______
vibrates

25. The maximum displacement of particle in vibratory motion is called ______.
amplitude

26. Light moves as _____ wave
transverse

27. Sound travels through gases as ______ waves
longitudinal

28. A wave transmits ______ through the medium
energy

29. the unit of frequency is ______.